The present invention relates to a submersible lens fiberoptic assembly for use in a biological environment, and especially to a submersible ball lens fiberoptic assembly for photodynamic therapy treatments (hereinafter referred to as PDT) for transferring radiation from an optical fiber to surrounding tissue.
There are three existing types of fiberoptics used for light delivery in PDT treatments. These three known arrangements are shown in FIGS. 1A, 1B and 1C.
FIG. 1A shows an arrangement known as a cylindrical diffuser. In this, a cylindrical optical element 11 is butted against an optical fiber 12, and functions to cylindrically diffuse light coupled into it via the optical fiber.
FIG. 1B shows a prior art arrangement known as a spherical diffuser. In this, a spherical optical element 13 is coupled to an optical fiber 14 by an optical coupling 15, and functions to spherically diffuse light from the optical fiber into surrounding tissue.
One disadvantage of the prior art constructions shown in FIGS. 1A and 1B is that every spot light source on the diffusing material emits light in a random direction; that is, there is no localization control over the specific tissue being treated.
A third prior art arrangement is shown in FIG. 1C, this being an arrangement known as a submersible microlens. In the arrangement of FIG. 1C light rays are emitted at a controlled divergence due to the functions of lenses. In this construction, a housing 16 encloses a miniature lens 17, and the housing is closed by a transparent cover plate 18. The end of an optical fiber 19 is positioned at the back focal point of the lens 17. The location of the back focal point of the lens is influenced by the index of refraction of the lens and of the medium in contact with the lens and the optical fiber surface. In the construction shown in FIG. 1C, the back focal point is fixed by sealing the fiber and lens in air through use of the housing 16 and window or cover plate 18. When this assembly is submerged in water or a saline solution, the beam divergence is reduced but the end or face of the optical fiber remains in focus since the medium surrounding the curved refracting surface of the lens is unchanged.
The ideal assembly for coupling radiation from an optical fiber into tissue is one which produces a highly divergent beam of light whose cross section everywhere, in air or water, is a magnified image of the optical fiber end or face. While the arrangement of FIG. 1C does achieve many of these objectives, the construction is complicated and accordingly expensive to manufacture.